This invention relates to a strap cutting tool of the type used to cut tensioned strapping and is particularly concerned with a new and improved arrangement for preventing uncontrolled release of the severed ends of the strapping upon severing.
Tensioned strapping is frequently employed for various purposes such as banding articles together for shipment. For example the strapping may be used to band together a stack of plywood sheets. In order to provide a satisfactory banding it is often necessary that substantial tension be imparted to the strapping, and therefore it is common to use metal as the strapping material. In order to tension the strapping it is also common to use powered tools which operate to tightly draw the strapping around the bundle and to secure the strapping in place. Tensions on the order of thousands of pounds can be imparted to steel strapping.
The common procedure for severing the strapping is by use of a severing tool, for example a pliers-type strap cutter. Because of the substantial tension force which can be imparted to metal strapping, care must be taken when using a severing tool because of the sudden release of tension which occurs upon severing. In the tensioned strapping, energy previously imparted to tension the strapping is stored as potential energy. Upon severing this energy is virtually instantaneously transformed into kinetic energy. The consequence is that the severed ends of the strapping separate extremely rapidly from each other in what can be an uncontrolled, violent whipping action. The particular nature of the whipping action will be a function of the tension which has been imparted to the strapping and the character of the strapping itself. If care is not exercised it is entirely possible for uncontrolled whipping of the severed ends of the strapping to be a potential source of damage and/or injury.
Previous devices have been added to strap cutting tools for the purpose of attempting to guard against uncontrolled release of the strapping upon severing. Examples are shown in U.S. Pat. Nos. 3,058,213; 3,237,302; and 3,237,303.
The present invention is directed to a new and improved strap cutting tool in which the energy of tension in the strapping which is released upon severing is absorbed before it can result in uncontrolled whipping of the severed ends of the strapping from the tool. The present invention involves the provision of energy absorbing structures, and a strategic configuration and arrangement thereof, on the strap cutting tool so that the energy which is released upon severing is substantially absorbed and dissipated by the energy absorbing structures with the result that violent uncontrolled whipping of the severed ends of the strapping is avoided. The present invention arises in part through the recognition and analysis of the detailed action which occurs in the strapping and cutting tool during the severing action. In consequence of this recognition and analysis energy absorbing structures have been created which are effective to absorb a substantial portion, indeed substantially all, of the energy which is released in the strapping upon severing so that little residual energy, if indeed any, remains in the strapping. The result is avoidance of uncontrolled whipping of the strapping out of the cutting tool.
In the preferred embodiment of the invention which is disclosed herein the energy absorbing structures comprise elastomeric elements which are mounted on the tool on lateral sides of the cutting mechanism. An opposite portion of the tool has anvil portions, and the anvil portions and the energy absorbing elastomeric elements are cooperatively arranged and constructed to forcefully hold the strapping throughout the operation of the cutting mechanism up to the point of severing, and upon severing the elastomeric elements absorb the released energy. The elastomeric elements are configured to have substantial columnar strength in the direction of force application to the strapping so that as the cutting mechanism is operated and the elastomeric elements are compressed in the direction of force application to the strapping, they retain their general configuration so as not to become unstable, much as a column subject to axial overloading might become unstable. Yet, the configuration of the elastomeric elements is such that the elements themselves also provide energy absorbing structure which absorbs the energy which is released in the strapping upon severing. This occurs with the elastomeric elements yielding laterally away from the cutting mechanism upon severing of the strapping. The elastomeric elements have friction faces which have friction contact with the strapping and the frictional forces which exist between the friction faces and the strapping result, upon severing, in the friction faces being displaced laterally with the strapping and their operation of the energy absorbing body portions of the elastomeric elements such that said body portions absorb the energy which is released in the strapping so that said energy does not appear in the form of violent uncontrolled whipping of the severed ends of the strapping from the cutting tool. With the invention a cutting tool can be used to sever strapping in which the tension can run to the order of thousands of pounds; for example as much as 6,000 pounds tension can be handled.
The cutting blade is also configured to perform a severing action which minimizes any tendency for the strapping to be ejected from the cutting mechanism by the severing action. While the invention may be practiced with other forms of cutting mechanisms, the disclosed cutting blade configuration promotes a more advantageous severing action both independently and cooperatively with the energy absorbing structure. The disclosed preferred embodiment also has certain specific constructional features which are advantageous. The invention may be embodied in a new cutting tool or can be used to modify an existing cutting tool.
The foregoing features, advantages and benefits of the invention, along with additional ones, will be seen in the ensuing description and claims which should be considered in conjunction with the accompanying drawings. The drawings disclose a preferred embodiment of the invention according to the best mode contemplated at the present time in carrying out the invention.